By JACK CHANG

Before the drums and chanting began, retired seamstress Rosa Silva Cardoso seemed to be the gentle octogenarian as she sat in a folding chair and greeted a steady stream of well-wishers in the back of the worship space she runs.

That changed when this temple of the Afro-Brazilian religion Umbanda exploded into frenetic activity. With the drums pounding out an ever more hypnotic beat, Cardoso entered a trance and, after a quick costume change, began twirling over the wood floor in a ruffled black and red dress. Onlookers said she'd been possessed by the spirit of a gypsy.

Since Umbanda began a century ago, millions of Brazilians have undergone similar possessions while practicing Brazil's most popular folk religion in neighborhood temples.

People have embodied African gods, Brazilian folk heroes and even underworld figures as the drums and incense drove them on. They've also come to such temples to receive the treasured counsel that those entities are known to give.

At Cardoso's temple, worshipers groaned and writhed as they were possessed by the devilish spirit of Exu. A tall, lanky man instantly became the malandro, or the rogue, which meant prancing around in a straw hat while puffing on a cigarette.

''When the entity comes, I feel out of breath, and it's like I'm fainting,'' Cardoso said after the ceremony. ``All I need to do is open the door and let it in.''

Umbanda has been a natural fit for a country where many believe in the everyday presence of spirits and omens. What's drawn the interest of international scholars is the religion's unmistakably Brazilian bent, which has won it fame as the country's only home-grown faith.

Umbanda's Brazilian focus is most obvious in its pantheon of spirits, which includes popular folk figures such as the rogue, who's a fixture of street culture here; the freed slave known as the preto velho; and an indigenous warrior known as the caboclo, who can appear adorned with feathered headdresses and bows and arrows.

Worshipers also can be possessed by someone from the northeastern Brazilian state of Bahia, a cowboy from southern Brazil or a poor ranch hand. In its use of Brazilian folk mythology, it'd be as if worshipers in the United States were possessed by cowboys, astronauts and blues singers.

''It developed as Brazilian cultural nationalism was growing, and people were interested in what it meant to be Brazilian,'' said Diana Brown, an associate professor in anthropology at Bard College in Annandale-on-Hudson, N.Y., who has studied Umbanda. ``There was an effort to make this a Brazilian religion.''

According to the religion's folklore, Umbanda took off after a teenager near Rio de Janeiro was possessed by an indigenous spirit known as the Caboclo das Sete Encruzilhadas, or the Indian of Seven Crossroads, in 1908.

That event launched what would become a potent mix of African religions, Roman Catholicism and the teachings of 19th-century French spiritualist Allan Kardec. The religion now claims as many as eight million devotees and more than 100,000 temples around Brazil.

Many temples are holding special ceremonies this year to celebrate the religion's centennial, which is as much about survival as it is about spirituality.

Throughout the early 20th century, Brazilian governments, alarmed at the religion's intense ceremonies, outlawed its practice, forcing many worshipers underground. Although the religion is legal now, Brazil's mushrooming Pentecostal churches still regularly condemn Umbanda and other Afro-Brazilian religions as the work of the devil.

Armando Fernándes, the president of a temple in a poor Rio de Janeiro neighborhood, said that such persecution shows a lack of understanding of the religion and its ceremonies. He spoke while embodying an indigenous spirit known as the Seven-Arrows Indian.

''We've suffered a lot of discrimination, but people just need to understand us,'' Fernandes said in the heavy lisp that's characteristic of the indigenous spirit. ``We're helping communities in need of spiritual healing.''

According to Zumira dos Santos Magalhaes, a manicurist who visited Cardoso's temple, many attend Umbanda ceremonies to ask counsel from spirits on everyday problems.

At Friday's ceremony, dozens of people paid $4 each to ask worshipers embodying the spirits about everything from how to get a pay raise to what to do about an unfaithful spouse. The questions commonly sparked long discussions reminiscent of therapy sessions.

''Each entity speaks in a different way with different words, so you have to figure out what they mean,'' Magalhaes said. ``But their advice helps a lot of people.''

Cardoso said she joined the religion at age 17 after a possessed worshipper held her hands and cured her of a mysterious illness. She said she hasn't been sick in the nearly seven decades since then, a miracle she credits to the spirit world.

''Everyone has their faith, and Umbanda has been the faith of many Brazilians for many years,'' she said. ``And it's worked for many of us.''